HARDNESS

Hardness qualifies the capacity of a material to resist to deformation. The testing methods to determine hardness are:

the Brinell test: we study the penetration, under an effort F, of a ball of diameter D in material; one measures the diameter D of the print and one calculates surfaces S of the segment of a sphere; one

HB ( Brinell hardness) = F/S

the Rockell test: we measure successively the penetration (e) of a conical point diamond t 120° for an effort F0 (e0), F1+ F0 and F0 (e2) (remanence). We calculates e3=e2-e0, E=e3/0,002, and one poses HRC (Rockell hardness) = 100-E

the Vickers test: we study the presentation of diamond of pyramidal form at square base under an effort F, during a given time; we measure the dimension of a diagonal (d), we calculate the surface of the print S, and we pose HV (Vickers pyramid hardness) = F/S

the Shore test; we release a ball of mass (m) and of diameter D, of a height H, we measure the height of rebound h. The energy of the fall is absorbed by a plastic deformation (without print) of the matter.